The present invention relates to a method and apparatus for handling and processing wafer-like materials. In particular, the invention relates to a method and apparatus for handling and processing thin wafers, such as semiconductor substrates. The apparatus of the present invention can be used in systems for such purposes as etching of semiconductor wafer substrates and sputtering of deposits on such substrates.
Known designs for wafer processing machines allow wafers to be processed in vacuum environments. Generally, it is often necessary to perform sequentially more than one process on a substrate. For example, it may be necessary, after the wafer is introduced into the vacuum environment, to etch the wafer for preparing a surface for subsequent process steps. The next step may be the sputtering of a first metallic layer on the substrate and a further sputtering deposition step or steps may then follow. In each case, different gases may be introduced into the chamber for the different sputtering steps and different cathode target materials are used, depending on the material to be deposited onto the substrate. Accordingly, different gaseous and plasma conditions are present for the different process steps. Generally, the prior art devices cannot allow simultaneous processing by different processes using different gaseous atmospheres of more than one wafer at a time, because once wafers are introduced into the vacuum chamber, only that particular process using that particular gas can be performed on the wafers in the chamber. If more than one process is carried out simultaneously on different wafers using these apparatus, cross contamination of the vapors and gases from the different processes may occur. Accordingly, it is not possible in these prior art arrangements to process more than one wafer at a time if different processes using different gases are to be performed upon the wafers. Thus, for example, in these prior art machines which have a plurality of processing stations, if it is desired to operate with, for example, a first gas on a first of the wafers and a second gas on a second wafer, such would not be possible simultaneously. Instead, the entire vacuum chamber would have to be purged of the first gas and the second gas introduced before the second wafer could be processed. Additionally, if a process step is to be performed on only some, but not all, of the wafers in the chamber, because all wafers are exposed to the same environment, there is the possibility of contamination of those wafers which are not being processed.
Furthermore, it is also important that the wafers be processed without transfer of the wafer between different handling mechanisms once in the vacuum chamber. Generally, the wafers to be processed in apparatus of the present invention are fragile, and to avoid particulate formation or breakage, it is preferable to avoid transfer of the wafer between different transfer mechanisms.
Additionally, in wafer processing machinery, especially machinery employing sputtering devices, it is necessary to change cathodes and targets of the sputtering devices, for example, to replace a target which has been substantially used. The cathodes in sputtering equipment generally include means for providing electromagnetic fields around the target of a particular orientation and a target of the material to be sputtered which is biased at high voltages with respect to the support structure and the substrate upon which the deposits are made. This causes the material of the target to vaporize into a plasma and be deposited upon the substrate. Where it is desired simultaneously to process a plurality of substrates in different gaseous environments, it is convenient to be able to replace only that particular target which requires replacement without disturbing the controlled environments in other process chambers in which the other substrates are disposed.